JEE Main & Advanced Mathematics Definite Integration Question Bank Fundamental definite integration, Definite integration by substitution

  • question_answer
    \[\int_{0}^{a}{{{x}^{2}}\sin {{x}^{3}}\,dx}\] equals                                           [RPET 1996]

    A)                 \[(1-\cos {{a}^{3}})\]     

    B)                 \[3(1-\cos {{a}^{3}})\]

    C)                 \[-\frac{1}{3}(1-\cos {{a}^{3}})\]               

    D)                 \[\frac{1}{3}(1-\cos {{a}^{3}})\]

    Correct Answer: D

    Solution :

               \[I=\int_{0}^{a}{{{x}^{2}}\sin {{x}^{3}}dx}\]; Put \[{{x}^{3}}=t\Rightarrow {{x}^{2}}dx=\frac{dt}{3}\]                    \[\therefore \,\,\,I=\frac{1}{3}\int_{0}^{{{a}^{3}}}{\sin t\,dt}=-\frac{1}{3}[\cos t]_{0}^{{{a}^{3}}}=-\frac{1}{3}[\cos {{a}^{3}}-1]\]                                        \[=\frac{1}{3}[1-\cos {{a}^{3}}]\].


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